How do I customize hashing and equality with std::forward_list?

Customizing hashing and equality in C++ using std::forward_list can enhance the way you manage collections of objects in scenarios where you require unique identifiers for storage in hash tables. Here's a guide on how to implement this effectively.

#include <iostream>
#include <forward_list>
#include <unordered_map>
#include <functional>

struct CustomData {
    int id;
    std::string name;

    // Equality operator
    bool operator==(const CustomData& other) const {
        return id == other.id && name == other.name;
    }
};

// Hash function for CustomData
struct CustomHash {
    std::size_t operator()(const CustomData& data) const {
        std::size_t h1 = std::hash()(data.id);
        std::size_t h2 = std::hash<:string>()(data.name);
        return h1 ^ (h2 << 1); // Combine the two hash values
    }
};

int main() {
    std::forward_list myList = { {1, "Alice"}, {2, "Bob"}, {3, "Charlie"} };
    std::unordered_map myMap;

    for (const auto& item : myList) {
        myMap[item] = "Some value associated with " + item.name;
    }

    // Output values based on CustomData
    for (const auto& pair : myMap) {
        std::cout << pair.second << std::endl;
    }

    return 0;
}